Laboratory apparatus including microscope slides, microtiter plates, vials, flasks, test tubes, syringes, coverslips, films and porous substrates, and assemblies comprising such devices, are often used to handle, measure, react, incubate, contain, store, restrain, isolate and transport important and sometimes minute volumes of liquid, particularly biological samples. Often there is a need to mark the apparatus to prevent confusion among samples when working with multiple samples. Accordingly, there is a need for a marking surface on a laboratory apparatus.
It is well known to frost a portion of the surface of a laboratory apparatus to form a marking surface. The frosted area is created by sandblasting, acid etching, mechanical abrading, or other methods of roughening the surface of the apparatus to create a surface which may be marked with a pen, pencil, or other marking instrument. Despite the matte finish of a roughened marking surface, permanent marking of the apparatus is nonetheless not assured.
The aforementioned techniques create a frosted surface by removing material from the apparatus surface, which necessarily results in a marking surface which is recessed from, or no higher than, the surface of the apparatus. The marking surface therefore does not provide a means of spacing stacked flat apparatus, for example, microscope slides. In addition, the marking surface is not provided with a pronounced background to contrast with marking material marked thereon.
Coating formulations which can be applied to a laboratory apparatus to form a marking surface are also known. A raised marking surface for a microscope slide is disclosed in U.S. Pat. No. 4,481,246 to Melisz et al. This patent discloses a resin-based coating having a sufficient amount of granular medium to impart porosity to the coating. To impart porosity, however, very high loadings of the granular medium are required; otherwise, the liquid epoxy in the formulation engulfs the granular medium and forms a smooth non-porous texture at the exposed surface of the coating. The high loadings of granular medium require the formulation to be highly viscous and have a limited range of rheological properties. Heavily loaded coatings are weakened or embrittled by the presence of large amounts of clay or pigment, and the permanence of a marking material applied to the surface may be compromised by marking and handling the coating. Furthermore, because so much of the coating formulation comprises granular medium, the chemical resistance afforded by the epoxy resin is diminished relative to the chemical resistance afforded by a coating comprising more substantial amounts of resinous material. Coatings which are believed to be made in accordance with the teachings of U.S. Pat. No. 4,481,246 to Melisz et al. are not chemically resistant to sodium hydroxide solutions and are measurably weakened by exposure to hydrochloric acid solutions in ethanol, boiling deionized water, xylene, and ethanol. In addition, coatings made in accordance with the patent may chalk, that is, the surface may break down to a powder upon contact with a marking instrument, which is especially undesirable in surfaces for identifying a sample or retaining a biological sample.
The surfaces of laboratory apparatus, for example, petri dishes, microscope slides and microtiter plates are often treated to enable the growth, manipulation and maintenance of cell cultures. These superficial treatments include exposure of plastic surfaces to electromagnetically generated plasmas using various gases or exposure of glass surfaces to silanizing liquids and gases. Often, the aforementioned exposure steps are followed by the application of coatings of extracellular matrix proteins. Cell types have been coated to a surface of a laboratory apparatus and maintained and/or grown by the effusion of nutrients and cell factors to their attached surfaces. Some cell types benefit from a cavernous or cave-like topology.
Superficial, and generally monomolecular treatments of laboratory apparatus to provide cell growth surfaces do not allow the effusion of nutrients or cell factors at their interface with cells, nor do they have a porous topology. It is desirable to provide a coating for a laboratory apparatus that allows the effusion of nutrients or cell factors at the interface of the coating and cells, and which has a porous topology.
There is a need for an even more permanent marking surface for laboratory apparatus, and for a formulation that provides more permanence and better rheological properties including thixotropy and viscosity. There is a need for a coating formulation that can be applied by a pad printing technique to provide a marking surface. There is a need for a coating formulation that can be printed onto a laboratory apparatus to form a biological sample-retaining coating useful for growing and analyzing a biological sample. There is also a need for a permanent coating material for laboratory apparatus which can promote the growth, life, maintenance or preservation of a biological sample.
The present invention provides a formulation which can be applied to a laboratory apparatus and dried or cured to form a coating having a porous surface. The present invention also provides a laboratory apparatus having a porous surface which can be used as a marking surface for substantially permanent marking applications. The present invention also provides a laboratory apparatus having a porous coating which can be used for retaining a biological sample.